A landscape of massive spherical boulders are the main attraction in this Kansas State Park.

The highest bridge in America was built for an almost unnervingly small amount of money.

When ecosystems collide in the arid Southwest.

The highest point in Oklahoma used to be a lawless outlaw's paradise.

A multi-storied adobe complex has been inhabited for more than a thousand years.

This crumbling UFO is one of only a few remaining "moveable ski chalets" of its kind.

A dormant lightning machine equal to all the power in Russia.

The world's second largest single-dish radio telescope, once used to contact E.T.

This limestone cave offers an incredible view of the Río Grande de Arecibo valley.

The world's brightest bioluminescent bay.

The smallest pub in Britain was once a cabinet of curiosities and it still has the dead cat to prove it.

The superstar of Cold War nuclear bunkers has been featured in countless films but is now barely operational.

Stepping away from the glitz of mobsters and casinos to learn about the other history of Vegas.

"Not too many people can say they've had a nuclear bomb dropped on them, not too many would want to." — Walter Gregg.

This astonishingly geometric cave has inspired everyone from Jules Verne to Pink Floyd.

Stalactites and stalagmites in a beautifully lit cave.

A massive underwater sinkhole made famous by Jacques Cousteau.

A battle between nature and architecture in the Cambodian jungle.

An ancient capital city that dates back 3,000 years old and harbors many surprises.

The oldest farmer's market in America is so ancient it was approved by the King of England.

An indoor miniature village and labor of love for Laurence Geiringer, a model railroad enthusiast.

This expansive bridge in the Canadian wilderness was originally just built for friends.

A famed drink seasoned with an amputated toe, now on its tenth digit.

A house turned museum is the real-life "home" of the fictional main character of The Wizard of Oz.